The YOB-431B is made of top quality aged and seasoned grenadilla wood for a rich 'professional' sound. This is the same material as used on our Custom models and it has been carefully crafted in a similar manner. It features accurate intonation, a balanced response, and an exquisite tone - truly professional quality at an intermediate model price. The 431B has a semi-automatic octave system and also includes a thumb plate. The keys are hand-adjusted by experienced artisans for precise playability.